U.S. patent application number 12/093058 was filed with the patent office on 2009-02-26 for composite material.
Invention is credited to Michael Ian Birrell.
Application Number | 20090053458 12/093058 |
Document ID | / |
Family ID | 35516713 |
Filed Date | 2009-02-26 |
United States Patent
Application |
20090053458 |
Kind Code |
A1 |
Birrell; Michael Ian |
February 26, 2009 |
Composite Material
Abstract
A formed thermoplastics composite sheet (100) having a laminated
structure wherein the laminate comprises at least a first (112) and
a second (114) cover layer, each being fibre reinforced, in between
which, in at least a portion of the sheet, there is provided a core
layer (106) comprising a deformable metallic element such that the
deformable element is arranged to reduce the elastic behaviour of
the thermoplastic composite (100) when compared to the sheet
without the deformable element.
Inventors: |
Birrell; Michael Ian;
(Hartfordshire, GB) |
Correspondence
Address: |
BOYLE FREDRICKSON S.C.
840 North Plankinton Avenue
MILWAUKEE
WI
53203
US
|
Family ID: |
35516713 |
Appl. No.: |
12/093058 |
Filed: |
November 6, 2006 |
PCT Filed: |
November 6, 2006 |
PCT NO: |
PCT/GB06/04118 |
371 Date: |
May 8, 2008 |
Current U.S.
Class: |
428/68 ;
156/60 |
Current CPC
Class: |
B62D 25/105 20130101;
Y10T 156/10 20150115; B60R 2021/343 20130101; Y10T 428/23 20150115;
B62D 29/043 20130101; B62D 29/001 20130101 |
Class at
Publication: |
428/68 ;
156/60 |
International
Class: |
B32B 3/02 20060101
B32B003/02; B31B 1/60 20060101 B31B001/60 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 10, 2005 |
GB |
0522960.4 |
Claims
1-33. (canceled)
34. A formed thermoplastics composite sheet having a laminated
structure wherein the laminate comprises at least a first and a
second cover layer, each being fibre reinforced, in between which,
in at least a portion of the sheet, there is provided a core layer
comprising a deformable metallic element such that the deformable
element is arranged to reduce the elastic behaviour of the
thermoplastic composite when compared to the sheet without the
deformable element.
35. A sheet according to claim 34 wherein each cover comprises a
plurality of sub-layers wherein the fibre reinforcement within each
sub-layer is substantially unidirectional.
36. A sheet according to claim 35 wherein each cover layer
comprises at least a first and a second sub-layers wherein the
fibre reinforcement within the first layer is arranged to be
substantially at 90 degrees to the fibre reinforcement in the
second sub-layer.
37. A sheet according to claim 34, wherein there is provided at
least one infill core layer, arranged in areas of the core layer
where there is no deformable metallic element.
38. A panel comprising a laminated plastics material structure
having at least a first cover layer and a second cover layer, each
of which is fibre reinforced, and in between which, in a least a
portion of the panel, there is provided a core layer comprising at
least one deformable metallic element wherein the introduction of
the deformable element is arranged to reduce the elastic behaviour
of the plastics material structure, when compared to the panel
without the element, such that the panel undergoes permanent
deformation during an impact.
39. A panel according to claim 38 in which the metallic element is
provided in any of the following forms: a braid, a wire, a
perforated plate, a mesh, a sheet.
40. A panel according to claim 38, wherein there is provided at
least one infill core layer, arranged in areas of the core layer
where there is no deformable element.
41. A panel according to claims 38 in which the cover layers each
comprises at least one fibre reinforced sub-layer having fibres
running in substantially a single direction.
42. A panel according to claim 38 in which each cover layer
comprises at least a first and a second sub-layers wherein the
fibre reinforcement within the first layer is arranged to be
substantially at 90 degrees to the fibre reinforcement in the
second sublayer.
43. A panel according to claim 38 in which each of the cover layers
each comprises the same, or at least a compatible, matrix material
compared to the core layer.
44. A panel according to claim 38 which is a vehicle body panel,
including a bonnet (i.e. a hood), a door, a roof panel.
45. A method of manufacturing a panel comprising: i. arranging at
least a core layer comprising a deformable element and a
fibre-reinforced cover layer on either side thereof; ii. applying
heat and pressure to consolidate the layers.
46. A method according to claim 45 in which the core layer extends
for less than the entire area of the panel.
47. A method according to claim 46 in which an infill-core layer is
provided in areas in which the core layer does not extend.
48. A method according to claim 47 in which the infill-core layer
is used to tailor the thickness of the panel to provide thickening
or thinning of the panel.
49. A method according to claim 45 in which the core layer is
provided as a matrix of plastics material containing the deformable
element.
50. A method according to claim 49 in which the matrix of plastics
material containing the deformable element is further defined as a
thermoplastic elastomer that is a mixture of in-situ cross linking
of EDPM rubber and polypropylene.
51. A method according to claim 45 which is used to produce a
vehicle body panel.
52. A method according to claim 45 wherein the deformable element
maintains a shape nearer a deflected shape than an original shape
after an impact.
53. A car body panel, such as a bonnet, comprising a consolidated
structure having at least a first cover layer and a second cover
layer, each being fibre reinforced, in between which, in a central
region of the panel there is provided a core layer comprising a
plurality of metallic wires arranged to deflect during an impact to
the panel such that the panel undergoes permanent deformation
during the impact.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a composite material,
particularly, but not exclusively, to a composite material arranged
to be used in a vehicle body panel.
BACKGROUND OF THE INVENTION
[0002] It is convenient to set the background of the present
invention with reference to the field of vehicle body panels
although it has wider applicability. It is know to fabricate car
body panels (such as the bonnet/hood) from a plastics material.
Generally, such a plastics body panel is made from a thermoset
composite but it is possible to manufacture such a panel from a
thermoplastic composite. In the case of thermoplastic composites
the panels tend to behave elastically during impacts (unless the
elastic limit is exceeded) such that they return to their original
shape. This can be disadvantageous during certain collisions such
as when the vehicle collides with a pedestrian or animal, etc. In
such instances the elastic behaviour can tend to launch the
pedestrian, etc. away from the vehicle thereby increasing his/her
injuries.
[0003] GB 305 694 shows a panel in which a polymer material is used
to protect a metal structural member positioned within the
polymer.
SUMMARY OF THE INVENTION
[0004] According to a first aspect of the invention there is
provided a thermoplastics composite material having a laminated
structure wherein the laminate comprises at least a first and a
second cover layer in between which, in at least a portion of the
material, there is provided a core layer comprising a deformable
element.
[0005] It is believed that a thermoset material would not be
suitable for embodiments of the invention since they are likely to
be too brittle, and therefore not ductile enough, such that they
will tend to fail upon an impact.
[0006] According to a second aspect of the invention there is
provided a panel comprising a laminated plastics material structure
having at least a first cover layer and a second cover layer, in
between which, in at least a portion of the panel, there is
provided a core layer comprising a deformable element arranged to
undergo permanent deformation during deformation of the panel.
[0007] Generally the panel is a vehicle body panel. However, this
need not be the case and the panel may be any panel which may
suffer from an impact.
[0008] According to a third aspect of the invention there is
provided a method of manufacturing a panel comprising [0009] i.
arranging at least a core layer comprising a deformable element and
a cover layer on either side thereof; [0010] ii. applying heat and
pressure to consolidate the layers.
[0011] Generally, the method will be used to manufacture vehicle
body panels. However, this need not be the case and the method may
be applied to any panel. which may suffer from an impact.
[0012] According to a fourth aspect of the invention there is
provided a method of manufacturing a composite material comprising:
[0013] i. arranging at least a core layer comprising a deformable
element and a cover layer on either side thereof; [0014] ii.
applying heat and pressure to consolidate the layers.
[0015] The core layer may comprise a thermoplastics material matrix
in which a deformable element is arranged. Such a matrix is
convenient because it may improve the adhesion between the cover
layers to adhere and the deformable elements.
[0016] The core layer may comprise a material provided by Bekaert
under the Trade Mark Santoprene.
[0017] According to a fifth aspect of the invention there is
provided a car body panel, such as a bonnet, comprising a laminated
plastics material structure having at least a first cover layer and
a second cover layer, in between which, in a central region of the
panel there is provided a core layer comprising a plurality of
metallic wires arranged such that the panel undergoes permanent
deformation in the central region during an impact thereto.
[0018] According to a sixth aspect of the invention there is
provided a method of reducing pedestrian injuries comprising
providing a vehicle with a body panel according to the fifth aspect
of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] There now follows by way of example only a detailed
description of embodiments of the present invention with reference
to the accompanying drawings of which:
[0020] FIG. 1 schematically shows an exploded view of the layers
within a formed composite sheet according to an embodiment of the
invention;
[0021] FIG. 2 schematically shows an enlargement of one of the
layers shown in FIG. 1;
[0022] FIG. 3 schematically shows a vehicle body panel in which a
portion comprises a composite material according to an embodiment
of the invention;
[0023] FIG. 4 schematically shows a section through the body panel
along line A of FIG. 3; and
[0024] FIG. 5 schematically shows various forms in which a
deformable element may be provided.
DETAILED DESCRIPTION OF THE DRAWINGS
[0025] The formed composite sheet 100 shown in exploded form
comprises, in this embodiment, five layers 102 to 110. In other
embodiments there may be other numbers of layers.
[0026] In this embodiment the topmost two layers 102,104 together
provide what may be termed a first cover layer 112; i.e. the cover
layer comprises two sub-layers. The bottommost two layers 108,110
together provide what may be termed a second cover layer 114; and
again comprises two sub layers. There may be other numbers of
sub-layers within the cover layers. In between the first 112 and
the second 114 cover layer there is provided a core layer 106 which
comprises a deformable element.
[0027] In it's widest sense the deformable element that is
incorporated in the composite sheet such that it substantially
stops, or at least reduces, the composite sheet from exhibiting
elastic behaviour. For example embodiments may be arranged such
that the sheet undergoes permanent deformation during an impact.
There may be some recovery from the deformation (i.e. partial
elastic behaviour) but the deformable element may largely reduce
the recovery thereby helping to prevent energy being returned to
the object that impacted the sheet. It is known that thermoplastic
polymers have a `memory` and exhibit an ability to recover their
form after an impact. The introduction of a core layer comprising a
deformable element (which may be thought of as stiffer than the
cover layers) that does not have such a recovery property helps to
prevent, or substantially reduce, the overall recovery of the
panel.
[0028] Generally, the deformable element will comprise a metallic
matrix. The metallic matrix may usually be steel or a steel alloy,
but could equally be other metals/alloys, such as aluminium or the
like.
[0029] In the embodiment of FIG. 1 the layer 106 comprising the
deformable element is shown as comprising a plurality of metallic
wires without a surrounding matrix. This is one possibility
although the deformable element may be provided in a number of
forms as described elsewhere. Moreover, the deformable elements may
generally be provided within a thermoplastics material matrix in
order to facilitate the fabrication of the composite material. In
embodiments in which the deformable element is provided in a
thermoplastics material matrix it may be found that the plastics
material adheres better to the deformable element.
[0030] In some embodiments there may be provided a plurality of
core layers, which may or may not have other layers in between.
Such additional core layers may be used to tailor the properties of
the material/panel in which the material is used.
[0031] As shown in FIG. 1 each of the cover layers 112,114 may
comprise a plurality of sub-layers. In this embodiment each of the
cover layers is shown as comprising what is termed a 0/90 lay up of
fibre reinforcement; i.e. a first sub-layer having fibres oriented
at 0.degree. and a second sub-layer having fibres oriented at
90.degree. relative to the first sub-layer. Thus, the properties of
the cover layers 112,114 can be tailored as desired by appropriate
use of reinforcement.
[0032] Thus, the structure may be thought of as a composite lay-up
which has first and second cover layers together with a core layer
which itself comprises a deformable element. In such an embodiment,
the properties of a consolidated panel are different when compared
to the properties of each layer.
[0033] An advantage of using fibre reinforcement in the cover
layers is that increased thermal stability may be achieved. Such
stability may be advantageous in applications such as vehicle
panels where it is helpful if the panel does not undergo
significant expansion over its operational temperature range (the
extremes of which could run from -40.degree. C. to a solar loading
of 130.degree. C.). Further, panels may be exposed to ovens during
a painting process which can expose the panel to temperatures of on
the order of 200.degree. C. In view of the large temperature
ranges, it is therefore advantageous that embodiments of the
invention match the thermal expansion of the cover layers to that
of the metallic element. Such matching may be achieved by
appropriate arrangement of reinforcing fibres in the cover
layers.
[0034] Thermal stability may be further increased if
uni-directional fibres are used as a reinforcing element in the
cover layers. As such a sub-layer of the cover layer may comprise
reinforcing fibres running in substantially a single direction such
that the overall cover layer comprises fibres running in different
directions.
[0035] The sub-layers within each of the cover layers 112,114 (or
indeed the core layer) may comprise any of the following: a
pre-preg lay up of oriented fibre reinforcement; random fibre
reinforced thermoplastic; self reinforced polymer sheet; a quasi
isotropic lay-up of fibres; or a woven thermoplastic composite
matrix or the like. Provision of the cover layers, as shown in this
embodiment, is advantageous because it allows a generally smooth
top surface to be provided which masks any imperfections in surface
aspect caused by the deformable element in the core layer 106. Such
imperfections would generally be referred to as witness marks. Such
a generally smooth surface is beneficial in embodiments which are
intended for use as a vehicle body panel in order that a good paint
finish can be achieved on the panel (or indeed in other application
in which a high class finish of the panel is desired). The use of
substantially unidirectional fibres within a sub-layer of a cover
layer may increase the resistance to witness marks in the surface
of the panel.
[0036] In this embodiment the metallic deformable element may
comprise any one of the following: wire, cord, braid, perforated
sheet or mesh; wire, cord, braid, perforated sheet or mesh which
has been encapsulated in a thermoplastics material compatible with
the plastics material in the cover layers. FIG. 5 shows examples of
such embodiments: FIG. 5a shows a plurality of wires; FIG. 5b shows
a mesh, FIG. 5c shows a braid and FIG. 5d shows a perforated sheet.
Each of these, or other, deformable members may be provided within
a matrix.
[0037] FIG. 5e shows a plurality of wires 500 within a
thermoplastics material matrix 502. Any other form of deformable
element may also be provided in a similar matrix 502. Some
embodiments of the invention may comprise additional layers than
those shown in FIG. 1. There may for example be a plurality of core
layers comprising deformable layers. There may be additional sub
layers within each of the cover layers.
[0038] In some embodiments, for example as shown in FIG. 3, the
core layer comprising the deformable element may be provided in a
portion of the overall area. In such arrangement the deformable
element may be considered to be positioned in a localised area.
FIG. 3 shows a vehicle body panel 300 (for example a vehicle
bonnet/hood, a door, a wing, a roof panel, or the like) in which a
core layer comprising a deformable element is provided at a central
region 302 thereof. In alternative embodiments the deformable
element may be provided in a different region, such the front, rear
etc. In some embodiments the formed composite sheet may comprise
more that one deformable element, such as 2, 3, 4, 10 or any number
there between. Furthermore the composite sheet may comprise
deformable elements of alternative topologies, such a circular
shaped or the like. A person skilled in the art will readily
appreciate that different applications may require different
configurations and be able to adapt the composite sheet
accordingly.
[0039] In such embodiments, areas of the composite material/vehicle
body panel may comprise one or more infill-core 400 layers in
addition to the two cover layers 112,114 in areas in which the
deformable element is not provided. Such infill-core layers 400 are
advantageous in order to help ensure that the thickness of the
overall panel/composite material remains substantially constant, if
it is desired to have a constant thickness. Such infill-core layers
400 will generally comprise a thermoplastics material which is
compatible with the thermoplastics material in the cover layers
112,114, or indeed are substantially the same thermoplastics
material. The infill-core layers 400 may or may not be reinforced,
although FIG. 4 shows these layers to be reinforced with a randomly
oriented short fibre. Compatible is intended to mean that the
thermoplastics can mix with one another without affecting the
properties of either of the thermoplastics or of the combination.
In one case the compatible thermoplastics may comprise the same, or
substantially the same, polymeric material.
[0040] In some embodiments, an infill-core layer may be used, of an
appropriate thickness, in order to tailor the thickness of the
panel as desired. For example, if a thicker portion of the panel is
desired then a thicker infill-core layer may be used and if a
thinner panel is desired then a thinner infill-core layer may be
used.
[0041] An embodiment in which the deformable element covers less
than the area of the panel is shown in FIG. 2. The core layer 200
containing the deformable element is shown in a central region and
an infill-core layers 202, 204 is shown on each side thereof. In
the embodiment shown, the infill-core layers are reinforced with
random fibres within the plastics material matrix. Other
embodiments may not be reinforced or may be reinforced with other
known techniques.
[0042] A vehicle body panel 300 as for example described in
relation to FIGS. 3 and 4 may be advantageous since it allows a
panel to be provided which is substantially smooth and therefore
may allow a high class paint finish to be achieved. Furthermore,
the deformable elements allow the deformation characteristics of
the panel to be tailored. In some panels, it is advantageous if the
panel does not show elastic behaviour once it is deformed. For
example, in a vehicle bonnet/hood it has been found that injury to
pedestrians which have been hit by the vehicle can be increased if
the bonnet/hood springs back to its original shape (i.e. exhibits
elastic behaviour) because the pedestrian may be propelled by the
panel returning to its original shape increasing his/her injuries.
By appropriate selection of the deformable elements a composite
thermoplastics material panel may be provided which exhibits
permanent deformation and thereby should not propel a pedestrian in
this manner.
[0043] The thermoplastics material/vehicle body panel may be
fabricated as is known in the art by combining (often referred to
as laying up) a plurality of layers (e.g. in the example of FIG. 1
the layers 102-110) and then heating the layers to their melt
temperature and consolidating the structure under pressure.
Processes such as vacuum consolidation, pressing or the like may be
used to consolidate the composite into the required form. The
laying up may be performed automatically by machine in a high
volume process, or manually in a lower volume process. Thus, a
homologous structure results once the consolidation is
performed.
[0044] It will be readily appreciated that by consolidating the
panel this has the effect of substantially removing any gas pockets
within the composite. The result is a composite that is constructed
as a substantially solid material.
[0045] If the deformable insert is metallic, or another material
with a high thermal conductivity, it may be possible to use the
deformable element to conduct heat into the material for this
consolidation process.
[0046] Generally, a panel formed by the process outlined in this
embodiment does not have any areas of high curvature (e.g. a
vehicle bonnet/hood) and therefore the deformable insert need not
be deformed before the consolidation process; i.e. it may, in such
embodiment, be used in sheet form. In other embodiments, if there
were a higher degree of curvature it may be necessary to shape the
deformable element before the layers are laid up before the
consolidation process.
[0047] The thermoplastics material may be any suitable
thermoplastics material such as polypropylene, PET, PBT,
polycarbonate, nylon thermoplastic polyurethane or thermoplastic
material blends.
[0048] In the example of polypropylene as the thermoplastics
material in the cover and core layers the structure would be heated
to between roughly 180.degree. C. and 220.degree. C. with a
consolidation pressure of roughly 1 bar or greater. Other
thermoplastics materials may require other temperatures and
pressures as will be appreciated by the person skilled in the
art.
[0049] In one embodiment, the deformable core layer 106 is provided
as a layer provided by Bekaert under the name Santoprene.TM., which
in one embodiment comprises wire of diameter or roughly 1 mm
surrounded by a thermoplastics matrix. This is of a similar
structure to that shown in FIG. 5d. It will be readily appreciated
however that alternative materials may be used. Indeed the wire
diameter do not need to be 1 mm and may be 0.1 mm, 0.5 mm, 2 mm, 5
mm or any number there between. In such alternative arrangements,
the properties of the material of the deformable element, such as
the metal used, may dictate which geometry is best suited for the
application.
[0050] Although primarily described in relation to a vehicle body
panel, embodiments of the invention may also provide any panel
which may be subject to an impact. For example, a road sign, a
panel for a door, or the like.
[0051] A typical thickness of a panel according to an embodiment of
the invention is likely to be roughly in the range of between 1 mm
and 10 mm in thickness. More generally, the panel may be roughly 5
mm or less.
* * * * *